package com.hj.util;

import java.io.*;

import org.mozilla.intl.chardet.nsDetector;
import org.mozilla.intl.chardet.nsICharsetDetectionObserver;

/**
 * @author dehui dou
 * @date 2020/10/3 19:33
 * @description 文本文件编码探测工具类
 */
public class FileCharsetDetector {

    /**
     * @author dehui dou
     * @description 传入一个文件(File)对象，检查文件编码
     * @param file
     * @return com.hj.utils.FileCharsetDetector.Observer 文件编码，若无，则返回null
     */
    public static Observer guessFileEncoding(File file) throws FileNotFoundException, IOException {
        return guessFileEncoding(file, new nsDetector());
    }

    /**
     * @author dehui dou
     * @description
     * 
     *              <pre>
     * 获取文件的编码
     * &#64;param file
     *            File对象实例
     * &#64;param languageHint
     *            语言提示区域代码 @see #nsPSMDetector ,取值如下：
     *             1 : Japanese
     *             2 : Chinese
     *             3 : Simplified Chinese
     *             4 : Traditional Chinese
     *             5 : Korean
     *             6 : Dont know(default)
     *              </pre>
     *
     * @return 文件编码，eg：UTF-8,GBK,GB2312形式(不确定的时候，返回可能的字符编码序列)；若无，则返回null
     * @throws FileNotFoundException
     * @throws IOException
     */
    public static Observer guessFileEncoding(File file, int languageHint) throws FileNotFoundException, IOException {
        return guessFileEncoding(file, new nsDetector(languageHint));
    }

    /**
     * @author dehui dou
     * @description 获取文件的编码
     * @param file
     * @param det
     * @return com.hj.utils.FileCharsetDetector.Observer
     */
    private static Observer guessFileEncoding(File file, nsDetector det) throws FileNotFoundException, IOException {
        // new Observer
        Observer observer = new Observer();
        // set Observer
        // The Notify() will be called when a matching charset is found.
        det.Init(observer);

        BufferedInputStream imp = new BufferedInputStream(new FileInputStream(file));
        byte[] buf = new byte[1024];
        int len;
        boolean done = false;
        boolean isAscii = false;

        while ((len = imp.read(buf, 0, buf.length)) != -1) {
            // Check if the stream is only ascii.
            isAscii = det.isAscii(buf, len);
            if (isAscii) {
                break;
            }
            // DoIt if non-ascii and not done yet.
            done = det.DoIt(buf, len, false);
            if (done) {
                break;
            }
        }
        imp.close();
        det.DataEnd();

        if (isAscii) {
            observer.encoding = "ASCII";
            observer.found = true;
        }

        if (!observer.isFound()) {
            String[] prob = det.getProbableCharsets();
            // // 这里将可能的字符集组合起来返回
            // for (int i = 0; i < prob.length; i++) {
            // if (i == 0) {
            // encoding = prob[i];
            // } else {
            // encoding += "," + prob[i];
            // }
            // }
            if (prob.length > 0) {
                // 在没有发现情况下,去第一个可能的编码
                observer.encoding = prob[0];
            } else {
                observer.encoding = null;
            }
        }
        return observer;
    }

    /**
     * @author liaohongwei
     * @description: 文件字符编码观察者, 但判断出字符编码时候调用
     */
    public static class Observer implements nsICharsetDetectionObserver {

        /**
         * @Fields encoding : 字符编码
         */
        private String encoding = null;
        /**
         * @Fields found : 是否找到字符集
         */
        private boolean found = false;

        @Override
        public void Notify(String charset) {
            this.encoding = charset;
            this.found = true;
        }

        public String getEncoding() {
            return encoding;
        }

        public boolean isFound() {
            return found;
        }

        @Override
        public String toString() {
            return "Observer [encoding=" + encoding + ", found=" + found + "]";
        }
    }

}
